Would like some feedback on the grounding & cable gauge used to configure my stereo battery and start/house battery in my boat.

Note: I have an ACR but I did not show it in this diagram

Both batteries sit in the port and starboard lockers on either side of the motor

The 2/0 cable was existing cable from factory which was already in place and was going to the start battery on the port side rear locker before I started reconfiguring. So I am just using these cables in more appropriate places.

Thought it might be easier to run a 1/0 cable over from the House/Start battery to the Stereo battery negative terminal instead of trying to tie into the block of the motor which would be harder to connect.

Is there any resistance issues based on cable length difference from one battery ground compared to the other battery ground, or ground is ground?